While a traditional upright microscope magnifies an object with an observation tube, a digital microscope is an apparatus for magnifying, observing and measuring an object with a digital camera and a display device installed therein instead of the observation tube. Recently, there are great progresses in the improvements of the digital camera and the display device, and thereby, the digital microscope is also greatly improved and replaces the conventional upright microscope.
US Patent Publication No. 2003/0030747 discloses a microscope system having a bracket for connecting a lens tube of a microscope unit to a digital camera. U.S. Pat. No. 6,452,625 discloses an upright microscope system having a display device instead of an observation tube. The microscope system of U.S. Pat. No. 6,452,625 maintains a conventional objective lens, an objective lens revolver and an illumination device, and thus a continuous zoom function of a digital camera cannot be used for the microscope system, and a size reduction of the microscope system is limited. U.S. Pat. No. 7,248,282 discloses a digital microscope capable of focusing an image by analyzing images of an object.
FIG. 1 is a drawing which shows a conventional digital microscope. As shown in FIG. 1, the conventional digital microscope comprises a main body (controller) 10 and a microscope unit 40. The main body 10 includes a CPU (Central Processing Unit) 12, a display device 14, a memory 16, a SMPS (Switched-Mode Power Supply) 18, a camera I/F (Interface) 20, and a light output device 30 having a light source (for example, a light bulb) 32 and a light channel 34. The microscope unit 40 includes a digital camera 42 connected to the camera I/F 20, a light terminator 44 connected to the light channel 34, a lens tube 46 and a stand 48. In a traditional upright microscope, a magnification ratio is changed by selecting an objective lens by rotating an objective lens revolver which is an objective lens housing including two or more objective lenses. However, in the digital microscope shown in FIG. 1, a plurality of lens tubes 46 should be prepared according to a magnification ratio and/or an observation function of the digital microscope. For example, lens tubes 46 for a low, a medium or a high magnification ratio should be provided according to a magnification ratio of the digital microscope, and lens tubes 46 having a long distance focus function or a polarization function should be provided according to an observation function of the digital microscope. Also, various stands 48 corresponding to the various lens tubes 46 are necessary.
Generally, as shown in FIG. 1, the conventional digital microscope includes only one lens tube 46 of a specific magnification ratio and a specific observation function, and one stand 48. In the digital microscope, in order to change the magnification ratio, namely, in order to use different lens tube 46 and different stand 48, the light terminator 44 and the digital camera 42 which are connected to the original lens tube 46 must be detached from the original lens tube 46 and then re-attached to a new lens tube 46 having a different magnification ratio. The replacement process of the lens tube 46 is inconvenient for a user, and the replaced parts, for example, a lens tube 46, a digital camera 42 can be damaged by frequent replacements, which results in the decrease of the life time of the digital camera.